The overall objective of the research is to develop methods to use 19F NMR in concert with other methods to determine the structure of intercalative drug-DNA complexes. These methods would then provide structural information to serve as the basis for the design of potential new antitumor drugs. In the first two years of support, 19F NMR spectra have been used to determine the detailed equilibrium interactions between a fluorine substituted analog of ethidium bromide and the dinucleotide pdC-dG. Several other fluorinated ethidium analogs have been prepared. A 2,9-dimethyl analog of ethidium which is hoped will have quite improved ability to inhibit RNA synthesis has also been prepared and shown to bind to DNA. In the coming year several new analogs will be prepared. 19F and proton NMR will be used to characterize the complexes of analogs with pdC-dG and other dinucleotides and oligonucleotides. The results of these studies will be compared with DNA binding data obtained by conventional techniques with the aim of drawing conclusions about the effects of substitution on the structure of the intercalation complex. The ability of each analog to inhibit RNA and DNA synthesis in cell culture will also be studied, and when appropriate, samples will be submitted to NCI for in vivo antitumor testing.